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The focus of the current research is to examine whether mixed-frequency investor sentiment affects stock volatility in the China A-shares stock market.

Mixed-frequency sampling models are employed to find the relationship between stock market volatility and mixed-frequency investor sentiment. Principal analysis and MIDAS-GARCH model are used to calibrate the impact of investor sentiment on the large-horizon components of volatility of Shanghai composite stocks.

The results show that the volatility in Chinese stock market is positively influenced by B–W investor sentiment index, when the sentiment index encompasses weighted mixed frequencies with different horizons. In particular, the impact of mixed-frequency investor sentiment is most significantly on the large-horizon components of volatility. Moreover, it is demonstrated that mixed-frequency sampling model has better explanatory powers than exogenous regression models when accounting for the relationship between investor sentiment and stock volatility.

Given the various unique features of Chinese stock market and its importance as the major representative of world emerging markets, the findings of the current paper are of particularly scholarly and practical significance by shedding lights to the applicableness GARCH-MIDAS in the focused frontiers.

A more accurate and insightful understanding of volatility has always been one of the core scholarly pursuits since the influential structural time series modeling of Engle (1982) and the seminal work of Engle and Rangel (2008) attempting to accommodate macroeconomic factors into volatility models. However, the studies in this regard are so far relatively scarce with mixed conclusions. The current study fills such gaps with improved MIDAS-GARCH approach and new evidence from Shanghai A-share market.

The purpose of this paper is to investigate the impact of Federal Open Market Committee (FOMC) meetings and the changes of the target rates on stock market uncertainty.

Multivariate regression analysis is applied to the historical data of VIX, FOMC meetings and target rates. Subtle relations are revealed by further categorizing the FOMC meetings into being scheduled and unscheduled and distinguishing the signs of the changes in VIX and target rates. CPI and the prime rate are used for robustness test.

The authors first examine the relation between FOMC meetings and target surprises; the results indicate that unscheduled FOMC meetings heavily impact the target surprises. Then, the authors investigate the relation between FOMC meetings and VIX changes; the results show that both unscheduled and scheduled FOMC meetings impact VIX, where the impacts of scheduled FOMC meetings are more substantial. The authors also analyze the responses of VIX to the target surprises, and the results reveal that there is an asymmetric effect of target surprises on VIX, where the influences of the scheduled positive target surprises are more significant. Finally, by examining the relation between the FOMC meeting and the risk-neutral density of the VIX option, the authors conclude that both KURT and SKEW are more affected by unscheduled FOMC meetings.

Deeper dimensions of the relations between VIX, FOMC meetings and target rates are analyzed and more insightful understandings of such relations are gained.

The aim was to investigate the effect of normal load on the tribological performance of laser cladded FeCoCrMoSi amorphous coating, which might choose the appropriate normal load for the friction reduction and wear resistance.

A FeCoCrMoSi amorphous coating was prepared on 45 steel using laser cladding, and the tribological performance of obtained coating under the different normal loads was investigated using a ball-on-disk tribometer.

The FeCoCrMoSi amorphous coating is composed of M₂₃C₆, Co₆Mo₆C₂ and amorphous phases, where the M₂₃C₆ hard phase enhances the coating hardness to increase the wear resistance and the Co₆Mo₆C₂ with the vein shape forms the strong mechanical interlock to play the role of friction reduction. The average coefficients of friction of containing amorphous FeCoCrMoSi coating under the normal loads of 3, 4 and 5 N are 0.68, 0.65 and 0.53, respectively, and the corresponding wear rates are 17.7, 23.9 and 21.9 µm3•N⁻¹•mm⁻¹, respectively, showing that the appropriate normal load is beneficial for improving its friction reduction and wear resistance. The wear mechanism is composed of adhesive wear, abrasive wear and oxidative wear, which is attributed to the high hardness of amorphous coating by the amorphous phase.

The FeCoCrMoSi amorphous coating was first applied for the improvement of 45 steel, and the effect of normal load on its tribological performance was investigated.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2024-0304/

The purpose of this paper is to improve the salt spray corrosion and electrochemical corrosion performances of H13 hot work mould steel, Cr–Ni coatings with the different Cr and Ni mass ratios are fabricated using a laser cladding (LC), which provides an experimental basis for the surface modification treatment of H13 steel.

Cr–Ni coatings with the different Cr and Ni mass ratios were firstly fabricated on H13 hot work mould steel using a laser cladding (LC). The salt spray corrosion (SSC) and electrochemical corrosion performances of Cr–Ni coatings in 3.5 Wt.% NaCl solution were investigated to analyze the corrosion mechanism, and the effect of mass ratios of Cr and Ni on their corrosion mechanism was discussed.

The laser cladded Cr–Ni coatings with the different Cr and Ni mass ratios are composed of Cr–Ni compounds, which are metallurgically combined with the substrate. The SSC resistance of Cr–Ni coating with the Cr and Ni mass ratios of 24:76 is the highest. The electrochemical corrosion resistance of Cr–Ni coating with the Cr and Ni mass ratio of 24:76 is the best among the three kinds of coatings.

In this study, the corrosion resistance of laser cladded Cr–Ni coatings with the Cr and Ni mass ratios of 17: 83, 20: 80 and 24: 76 was first evaluated using salt spray corrosion (SSC) and electrochemical tests, and the effect of mass ratios of Cr and Ni on their corrosion mechanism was discussed.

The aim was to investigate the effect of Cr₃C₂ mass fraction the high-temperature tribological performance of laser cladded WC-10Co₄Cr coating, in which the Cr₃C₂ played the role in enhancing wear resistance.

The WC-10Co₄Cr-xCr₃C₂ (x = 5%, 10% and 15%) were prepared on H13 steel using laser cladding, and their coefficients of friction and wear rates at 500°C were investigated using a ball-on-disc wear tester.

The WC-10Co4Cr-xCr₃C₂ powders are composed of WC, Co₃W₃C, CoCr and Cr₃C₂ phases, and the defects such as pores and cracks are reduced by the addition of Cr₃C₂. The coefficient of friction and wear rats of WC-10Co4Cr-xCr₃C₂ coatings are decreased with the Cr₃C₂ mass fraction, showing that the addition of Cr₃C₂ significantly enhances the tribological properties of WC-10Co₄Cr coating. The wear mechanism is adhesive wear and oxidation wear, and the Cr₃C₂ plays the roles of friction reduction and wear resistance, which provides valuable insights into optimizing the performance of WC-10Co₄Cr coating.

The Cr₃C₂ was first added into the laser cladded WC-10Co₄Cr coating, which improved its high-temperature tribological performance.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2024-0471/

The purpose of this study to investigate the high temperature tribological performances of CrN and CrAlN coatings on AISI H13 steel, which was beneficial to improve the wear resistance of hot work molds.

Arc ion plating was used to deposit the CrN and CrAlN coatings on AISI H13 steel, and the tribological performances of CrN and CrAlN coatings were evaluated using a ball-on-plate wear tester.

The average coefficients of friction and wear rate of CrAlN coating in the normal wear period are 0.33 and 5.34 × 10^–9 mm³·N^–1·mm^–1, respectively, which are lower than those of CrN coating, exhibiting that the outstanding friction reduction. The formations of Cr and Al oxides during the wear process are the main factor in enhancing the tribological performance of CrAlN coating.

CrN and CrAlN coatings were applied for hot work molds, and their tribological performances were comparatively investigated.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-09-2024-0359/

This paper aims to investigate the effects of Cr and Ta additions on the friction performance and corrosion-wear mechanism of Fe90-Al₂O₃ coating in 3.5% NaCl solution.

Cr and Ta reinforced Fe90-Al₂O₃ coatings were prepared on Q235 steel by laser cladding. The effects of Cr and Ta addition on the coefficient of friction (COF) and wear rate of Fe90-Al₂O₃ coating were investigated using a friction tester, and the wear model was established to discuss its corrosion-wear mechanism.

The average COFs of Fe90-Al₂O₃, Fe90-Al₂O₃-10%Cr and Fe90-Al₂O₃-10%Ta coatings in 3.5% NaCl solution are 0.57, 0.42 and 0.75, respectively, and the corresponding wear rates are 9.42 × 10⁻⁷, 5.31 × 10⁻⁷ and 7.02 × 10⁻⁷ mm³ s⁻¹ N⁻¹, respectively. The corrosion-wear resistance of Fe90-Al₂O₃-10%Cr coating is the best among the three kinds of coatings, in which the additions of Cr and Ta play a role in solid solution strengthening.

The Fe90-Al₂O₃ coating was strengthened by the additions of Cr and Ta to improve its corrosion-wear resistance in 3.5% NaCl solution.

This paper aims to investigate the effect of Ti₃SiC₂ on the high-temperature tribological behaviors of NiCr coating, which was beneficial to improve the friction-wear performance of hot work mold.

NiCr-Ti₃SiC₂ coatings were prepared on H13 steel substrate by laser cladding. The microstructure, phases and hardness of obtained coatings were analyzed using a super-depth of field microscope, X-ray diffraction and microhardness tester, respectively, and the tribological performance of obtained coatings at 500°C was investigated using a high-temperature tester.

The results show the NiCr-Ti₃SiC₂ coatings are comprised of γ-Ni solid, solution, Ti_xNi_y, TiC and Ti₃SiC₂ phases, and the coating hardness is increased with the increase of Ti₃SiC₂ mass fraction, which is contributed to the fine-grain and dispersion strengthening effect by the addition of Ti₃SiC₂. The NiCr-Ti₃SiC₂ coatings present excellent friction reduction and wear resistance by the synergetic action of Ti₃SiC₂ lubricant and hard phase, and the wear mechanism is predominated by abrasive wear and oxidation wear.

Ti₃SiC₂ phase was used to reinforce the tribological performance of H13 steel at high temperature, and the roles of friction reduction and wear resistance were discussed.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2023-0004/

The purpose of this study was to develop a TiAlSiCN coating with high bonding and hardness, ultra-low friction and good lubrication characteristics, which provided an experimental basis for the surface modification of YT14 cemented carbide cutting tools.

In this work, a TiAlSiCN coating was deposited on YT14 cemented carbide cutting tool through cathodic arc ion plating. The surface-interface morphologies, distributions of chemical elements, phases, bonding energy and surface roughness were analyzed using field emission scanning electron microscopy, energy-dispersive spectroscopy (EDS), X-ray diffraction, X-ray photoelectron spectroscopy and atomic force microscopy, respectively, and the coating the bonding strength were quantitatively characterized with a scratch.

The average COFs of the TiAlSiCN coating at 700°C, 800°C and 900°C were 0.68, 0.57 and 0.38, respectively, showing that the TiAlSiCN coating was an effective lubricant at a high temperature, and the wear rate of the coating increases with wear temperature. After wearing at 700°C, 800°C and 900°C, the Ti, Si and N elements form atom-poor regions, while Al forms an atom-rich region, showing that the oxides of Ti, Al and Si are formed to improve the wear resistance of the coating. The wear mechanism of TiAlSiCN coating at high temperatures was composed of abrasive wear and oxidation wear.

The friction-wear behaviors of TiAlSiN coating were investigated using an HT-1000-type high-temperature friction wear tester, and the worn tracks on the coatings were analyzed using an EDS plane scan, thus obtaining the wear mechanism of TiAlSiN coating.

This study aims to investigate the influences of Al₂O₃ mass fraction on the corrosive wear and electrochemical behaviors of FeAl–xAl₂O₃ coatings.

FeAl–xAl₂O₃ coatings were prepared on S355 steel by laser cladding to improve its corrosive wear and electrochemical properties.

The average coefficients of friction and wear rates of FeAl–xAl₂O₃ coatings are decreased with the Al₂O₃ mass fraction, and the Al₂O₃ plays a positive role in the corrosion wear resistance. Moreover, the charge transfer resistance of FeAl–xAl₂O₃ coatings is increased with the Al₂O₃ mass fraction, showing the FeAl–15%Al₂O₃ coating has the best corrosion resistance. The findings show the corrosion resistance of FeAl–15%Al₂O₃ coating is the highest among the three kinds of coatings.

Al₂O₃ was first added into FeAl coatings to further improve its corrosive wear and electrochemical properties by laser cladding.